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A force model is presented to predict cutting forces in end milling. The helical end mill geometry model is established containing the cutting velocities and the cutting forces during the cutting process, which considers the pitch angle and the helix angle of each flute. The helical flutes are decomposed into a set of infinitesimal oblique cutting edges. At every oblique cutting element, the geometric angles and the cutting velocities are expressed in the three-dimensional plane and the differential cutting forces are determined by cutting energy in the effective cutting plane. By integrating the differential cutting forces along each cutting edge, which considers the effect of the feed velocity, the milling forces can be predicted. The proposed model has been verified with various cutting tests using regular end mill and variable helix end mill. The predicted and measured cutting forces are compared to illustrate the viability of the proposed cutting force model in end milling. [ABSTRACT FROM AUTHOR]

The microclimate of a desert oasis in hyperarid zone of China was monitored using micrometeorological methods and compared with those of areas adjacent to forested land. Differences in ground-level photosynthetically active radiation (PAR) on clear, cloudy and dust storm days and their subtending causes are analysed and discussed. Desert oases serve the ecological functions of altering solar radiation, adjusting near-ground and land surface temperatures, reducing soil temperature differences, lowering wind velocity, and increasing soil and atmospheric humidity. The total solar radiation in the interior of the oasis was roughly half of that outside a forest canopy. During the growing season, air temperatures in Populus euphratica Oliv. (poplar) and Tamarix ramosissima Ledeb. (tamarisk) forests were 1.62 °C and 0.83 °C lower respectively than those in the areas around the forests. Furthermore, the taller the forest cover, the greater the temperature drops; air temperatures in the upper storey were greater than those in the lower storey, i.e., air temperature rose with increasing height. Over the growing season, the relative humidities of the air in the poplar and tamarisk forests were 8.5% and 4.2% higher respectively than those in areas around the forests. Mean wind velocity in poplar-forested lands was 0.33 m s−1, 2.31 m s−1 lower than that in the surrounding area. During dust storm days the PAR was significantly lower than that on cloudy or clear days, when it was high and varied in an irregular manner. [ABSTRACT FROM AUTHOR]